4130 vs 1025 (mild) steel.

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Bobbyt
Posts: 24
Joined: Sat Jun 04, 2022 7:05 am

4130 vs 1025 (mild) steel.

Post by Bobbyt »

Hi folks.

Funny how lots has been written about this except what I really want to know.

Most of the fittings in the plans are of 1025 (mild) steel. We can use a piece of 4130 in place of the mild steel at the same thickness (13 gage lets say, or .090). BUT that defeats the purpose of using 4130. 4130 is stronger therefore we can use a thinner (lighter) piece. I have not seen anywhere in these forums where we have a definitive equivalent of 4130 and 1025 mild steel. Would a 13 gage of 1025 steel be the equivalent of a piece of .065 4130? .075 4130? .085 4130? Does anyone know FOR SURE what the equivalent is? Is there a chart? Calculation?

Much obliged.
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taildrags
Posts: 637
Joined: Tue Mar 07, 2017 10:39 pm

Re: 4130 vs 1025 (mild) steel.

Post by taildrags »

The short answer is "it depends". It depends on the shape of the part and the way the forces are acting on it. Each part that you intend to make out of 4130 instead of 1025 would have to be examined for how it's loaded, how it's attached, and its shape. But in most cases on this airplane, if you were to change the cross-sectional area or the thickness of a given part that's designed to fit into the assembly based on its dimensions, if you start changing the dimensions of the part, you're liable to find that there are other consequences of doing so. As in, things might not fit together the same way. And in many of those cases, once you change one thing, it requires adjustment of another... and sometimes another. The easiest thing is to just substitute the 4130 but leave the dimensions the same and everything will fit as per the plans and your build will go quicker and smoother.

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power
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KenBickers
Posts: 128
Joined: Tue Mar 07, 2017 7:00 pm

Re: 4130 vs 1025 (mild) steel.

Post by KenBickers »

Thinking back to when I was confronting this question, the rub occurred when the thickness of 1025, which if my memory hasn't totally failed me is called out in gauge units, did not exactly match the thickness options in 4130, which is called out in fractions of an inch.

What I did was select the thinner 4130 option, if (and this was the big "if"), the increase in strength in percentage terms from using 4130 meant that it should be at least as strong as the part if made from 1025. Otherwise I would opt for the next size up in 4130. All other dimensions were kept the same.

I'm not an aerospace engineer and at the time didn't have one handy. But that's how I sorted out the choice.

Cheers, Ken
Bobbyt
Posts: 24
Joined: Sat Jun 04, 2022 7:05 am

Re: 4130 vs 1025 (mild) steel.

Post by Bobbyt »

taildrags wrote: Sun Jan 22, 2023 10:30 pm
Thanks, Oscar. Some people sell "Pietenpol fittings" out of 4130, but thinner than what's called for in the plans and I wonder where they get their data. Ho well. I guess I'll substitute at the same thickness.

Thanks!


The short answer is "it depends". It depends on the shape of the part and the way the forces are acting on it. Each part that you intend to make out of 4130 instead of 1025 would have to be examined for how it's loaded, how it's attached, and its shape. But in most cases on this airplane, if you were to change the cross-sectional area or the thickness of a given part that's designed to fit into the assembly based on its dimensions, if you start changing the dimensions of the part, you're liable to find that there are other consequences of doing so. As in, things might not fit together the same way. And in many of those cases, once you change one thing, it requires adjustment of another... and sometimes another. The easiest thing is to just substitute the 4130 but leave the dimensions the same and everything will fit as per the plans and your build will go quicker and smoother.

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power
Bobbyt
Posts: 24
Joined: Sat Jun 04, 2022 7:05 am

Re: 4130 vs 1025 (mild) steel.

Post by Bobbyt »

Thanks for your thoughts on the subject. There are many areas in this build where one can allow their brains to get balled up in details like this!
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